Nondestructive readout for electrochemical storage cell

ABSTRACT

This invention is directed to a nondestructive readout system for an electrochemical storage cell using a second electrochemical storage cell in series with the first electrochemical cell and with the readout provided by passing a first current through both the first and second electrochemical cells so as to remove any information stored in the first cell while at the same time storing the same quantity of information in the second cell and then using a low-voltage source to provide a second current to the first and second cells in a direction to restore the information in the first cell while removing the information stored in the second cell and with the low-voltage source normally connected across the first and second cells.

United States Patent [54] NONDESTRUCTIVE READOUT FOR ELECTROCHEMICALSTORAGE CELL 9 Claims, 2 Drawing Figs.

52 U.S.Cl 340/l73CH, 324/94 5| lnt.Cl c11c27/00,

Gllc ll/00,Gllc 7/00 3,387,288 6/l968 Bissettetal 340/173 3,432,8143/1969 Bissett 340/173 3,521,045 7/l970 Murphy 340/173 R PrimaryExaminer-Bernard Konick Assistant ExaminerStuart Hecker Attorney-Smyth,Roston & Pavitt ABSTRACT: This invention is directed to a nondestructivereadout system for an electrochemical storage cell using a secondelectrochemical storage cell in series with the first electrochemicalcell and with the readout provided by passing a first current throughboth the first and second electrochemical cells so as to remove anyinformation stored in the first cell while at the same time storing thesame quantity of information in the second cell and then using alow-voltage source to [50] Field olSearch .i 340/173 R, provide a secondcurrent to the first and second cells in a173CH;324/94;3l7/230-232;204/5,194 direction to restore the informationin the first cell while removing the information stored in the secondcell and with 56] References Cited the low-voltage source normallyconnected across the first and UNITED STATES PATENTS second cells.$472,083 3/1965 Constantine 340/173 Inga/7 Z NONIDESTRUCTIVE READOUT FORELECTROCHEMICAL STORAGE CELL The present invention relates to thenondestructive readout of electrochemical storage cells. Theseelectrochemical storage cells include at least a pair of electrodes incontact with an electrolyte and the electrochemical storage cells alsoinclude an active material which is physically transferred between theelectrodes in the cell. Thisphysical transfer of active material may beused to provide for a storage of information. As a specific example,electrochemical cells of the type shown in copending application Ser.No. 519,634 now U.S. Pat. No. 3,423,648 filed on Jan. 10, 1966, in thename of Martin Mintz and assigned to the same assignee as the instantapplication may be used.

The electrochemical storage cells disclosed in the abovementionedcopending application are often included in monitoring systems toprovide for the storage of information by the transfer of activematerial within the cells. It is often desirable to provide for anondestructive readout of the information stored in the electrochemicalstorage cell, either in situ within the monitoring system or by removingthe cell and reading out the information stored in the cell using areadout unit. The present invention provides for the reading out of theinformation stored in the cell in a nondestructive way so that theinformation may be replaced in the cell.

The present invention accomplishes the nondestructive readout by using asecond electrochemical storage cell similar to the first cell. The firstand second electrochemical cells are connected in series with eachother. Information is stored in the first cell by applying aninformation signal to the first cell only and with the informationsignal in a direction to provide for the desired transfer of the activematerial between the electrodes in. the first cell. When it is desiredto readout the information now stored in the first cell, a secondcurrent is applied through both the first and second electrochemicalcells in a direction to remove the active material which had beenpreviously transferred by the information signal and to store a likeamount of active material in the second electrochemical storage element.

Therefore, even though the first electrochemical storage element has hadall of the active material retransferred during the readout, theinformation is not lost since this information is stored by a transferof active material in the second electrochemical storage cell. Thereadout current which is used to provide for the readout of theinformation stored on the first cell may be provided within themonitoring system or by any external type of readout device, forexample, a readout device such as shown in U.S. Pat. No. 3,387,288issued on June 4, 1968, or patent application Ser. No. 711,311, now U.S.Pat No. 3,518,501 filed on Mar. 7, 1968, in the name of Thomas B.Bissett and John Brain Murphy, both patent and patent application beingassigned to the same assignee as the instant application. The actualreadout of all of the information stored in the first cell may bedetermined when the voltage across the first cell rises and this rise involtage occurs because the resistance across the cell rises when all ofthe active material is removed from one of the electrodes in the cell.

The present application provides for a unique method of retransferringthe information back to the first electrochemical cell while removingthe information which has been stored in the second electrochemicalcell. The information is transferred back using a third flow of currentthrough the first and second electrochemical cells in a directionopposite to the second flow of current and with the current beingprovided by a low-voltage source normally coupled across both the firstand second electrochemical cells. Once the low-voltage source providesfor the transfer of all of the active material stored in the second celland provides for a transfer of active material in the first cell so asto reconstitute the information which was initially stored by theinformation signal, the lowvoltage source ceases to provide for anysignificant flow of current through the first and second electrochemicalcells.

This reduction of the third current flow to a negligible value occurswhen all of the active material is transferred from one of theelectrodes in the second electrochemical cell, and the resistance of thesecond cell therefore rises significantly. The rise in resistancedecreases the current flow in the circuit provided by the voltage sourceand the first and second electrochemical cells. Also, the source oflow-voltage normally has a value which is less than the maximum opencircuit voltage for the second electrochemical cell so that no damagecan occur due to the rise in voltage.

In a general embodiment of the invention, the first and secondelectrochemical cells are connected in series and a switch is providedso as to either connect the source of lowvoltage or a source of readoutcurrent to the first and second electrochemical cells. The switch isnormally in a position to connect the source of low voltage so that theswitch may be thrown to the position to provide a readout current andonce the readout has occurred the switch may be returned to its normalposition to allow the low-voltage source to replace the information inthe first electrochemical storage cell and to remove the informationstored in the second electrochemical cell.

In a specific example of a nondestructive readout circuit of the presentinvention, a computer which is designed to monitor drinking habits isdisclosed, which computer may be similar to that shown in copendingapplication Ser. No. 711,312, no'w U.S. Pat. No. 3,521,045 filed on Mar.7, 1968, in the name of John Brain Murphyand assigned to the sameassignee as the instant application.

A clearer understanding of the invention may be had with reference tothe following description and drawings wherein:

FIG. 1 illustrates a schematic of a nondestructive readout circuitconstructed in accordance with the teachings of the present inventionand which may be used to provide for the method of the presentinvention, and.

FIG. 2 illustrates a nondestructive readout circuit included in amonitoring system.

In FIG. 1, a nondestructive readout circuit is shown including a pair ofelectrolytic storage cells 10 and 12. The electrolytic storage cells maybe of the type shown in copending application Ser. No. 519,634 filedJan. 10, 1966, in the name of Martin Mintz. The electrochemical storagecell 10 is primarily used to store information and includes a pair ofelectrodes l4 and 16. The cell 10 also includes an active material 18for transfer between the electrodes. As an example, the electrode 16 maybe a storage electrode and, for example, the electrode 16 may be theouter container as shown in the copending application Ser. No. 519,634.The active material 18 is actually transferred between the electrodesthrough the use of an electrolyte which is in contact with theelectrodes 14 and 16.

Input information is applied from a pair of terminals 17 and 19 throughthe electrochemical storage cell 10 in a direction as shown by the arrow20. The input information, generally in the form of electrical current,passes through the electrochemical storage element 10 so as to transfera quantity of active material 18 from the electrode 16 to the electrode14. This transfer for active material is therefore in representation ofthe information and specifically the quantity of active materialtransferred depends upon the period of time the current 20 passesthrough the cell 10 and the amplitude of the current 20.

At times it is desirable to provide for a readout of this transfer ofactive material so as to determine the amount of information which hasbeen stored. Many times it is desirable to readout the information in anondestructive way so as to retain the information which has been storedin the cell 10.

The electrochemical storage cell 12 is useful in providing for thisnondestructive readout. The cell 12 also includes a pair of electrodes22 and 24 plus active material 26 for transfer between the electrodes inthe same manner as discussed above with reference to the cell 10. Again,the electrode 22 may actually be a storage electrode such as a containerelectrode so as to provide a reservoir of active material 26. Alsouseful in the nondestructive readout of the present invention is alowvoltage source 28, a resistance 30 and a switch 32. The switch 32 isnormally in the position shown by the solid line and is in the readoutposition when in the position shown by the dotted line.

Assuming that a particular quantity of information has been stored inthe cell and it is now desirable to provide for a readout, the switch 32is moved to the dotted position and a readout current is applied to theseries arrangement of cells 10 and 12 from output terminals 34 and 36.This readout current may be of any desirable type, for example, thereadout may be provided in a manner disclosed in U.S. Pat. No. 3,387,288or in copending patent application Ser. No. 71 1,31 l. The readout isaccomplished when all of the active material 18 previously transferredto the electrode 14 by the information signal is retransferred back tothe electrode 16. When all of the active material 18 is retransferred tothe electrode 16, the resistance of the electrolytic cell 10 rises andthis rise in voltage may be detected so as to disconnect the readoutcurrent. The direction of the readout current is as shown by the arrow38.

It can be seen that as the active material 18 is retransferred back tothe electrode 16, active material 26 is being transferred to theelectrode 24. Initially the electrode 24 did not have any activematerial and the quantity of active material 26 which is transferred tothe electrode 24 is determined exactly by the quantity of activematerial 18 which is retransferred back to the electrode 16. Therefore,while the readout current as represented by the arrow 38 is reading outthe information stored in the cell 10, the same quantity of informationas represented by the active material 26 is being stored in the cell 12.

After the readout is accomplished, the switch 32 may now be returned toits normal position as shown by the full line position of the switch.With the switch 32 in the normal position the low-voltage source 28provides for a flow of current through the series arrangement of cells10 and 12 in a direction as shown by the arrow 40. This current asrepresented by the arrow 40 operates to retransfer the active material26 back to the electrode 22 while at the same time transferring activematerial 18 from the electrode 16 to the electrode 14. When all of theactive material 26 is retransferred to the electrode 22, the samequantity of active material 18 is now present on the electrode 14 andreconstitutes the information stored in the cell 10.

When all of the active material 26 is retransferred from the electrode24 to the electrode 22, the resistance of the cell 12 rises, therebyproviding for an increase in voltage across the cell. Since the voltagesource 28 has a relatively low voltage, for example, 0.2 volt, and sincethe resistance of the circuit is greatly increased due to the rise inresistance of the cell 12, the current flow in the circuit clue to thevoltage source 28 is negligible. The value of the voltage source 28 isgenerally chosen to be within the maximum open circuit voltage that thecell 12 may be allowed to rise to when all of the active material isremoved from one of the electrodes. Depending upon the particular designof the cell, the value of the voltage source 28 is chosen so as not toprovide for an oxidation within the cell.

In FIG. 2, the nondestructive readout circuit of the present inventionis incorporated in a monitoring circuit, for example a circuit formonitoring the level of alcohol in the blood of a drinker. Themonitoring circuit may generally be of the type shown in copendingapplication Ser. No. 711,312 filed in the name of John Brian Murphy andassigned to the same assignee as the instant application. The monitor ofFIG. 2 includes first and second electrochemical cells 100 and 102,which cells have first and second electrodes and active material in thesame manner as the cells 10 and 12 in FIG. 1. The cell 100 is used tostore data while the cell 102 is used in the nondestructive readoutprocess.

Included in the circuit of FIG. 2 are a pair of voltage sources 104 and106. The voltage source 104 is generally of a higher value than thevoltage source 106 and specifically the voltage source 104 may have avalue of approximately 9 volts whereas the voltage source 106 may have avalue of approximately 1.5 volts.

The embodiment of FIG. 2 also includes a plurality of resistors whichare associated with the cells and 102 so as to control the amplitude ofthe current through these cells. Specifically, resistors 108 and 110,variable resistor 112 and resistors 114 and 116 are associated with thecells 100 and 102 at various times to control the current through thesecells. A pair of diodes 118 and 120 are used to drop the voltageproduced by the source of voltage 106 so that at the appropriate timethe voltage across the cells 100 and 102 is at a relatively low value,for example, equal to approximately 0.2 volt. A resistor 122 is coupledacross this series circuit of the voltage source 106 and the pair ofdiodes 118 and 120. Finally, a pair of switches 124 and 126 are used tocontrol the direction of the flow of current through the cells 100 and102.

A readout portion of the circuit is coupled to the cells 100 and 102through a switch 128. The switch 128 and the switch 126 are gangedtogether and, as designated in FIG. 2, the switches 126 and 128 havenormal" positions and have readout positions. The switches 126 and 128are normally maintained in the positions as shown in FIG. 2.

Coupled from the movable terminal of the switch 128 is the emitter of atransistor 130. A second transistor 132 is coupled from the collector ofthe transistor and a third transistor 134 is coupled form the collectorof the transistor 132. In addition, the readout circuit includes biasingresistors such as resistors 136, 138, 140, 142 and 144 plus loadresistors 146 and 148 and an output meter 150. A capacitor 152 iscoupled to the base of the transistor 134.

In a normal operation of the monitoring system of FIG. 2 there isinitially no active material which has been transferred inrepresentation of information in the cell 100 as well as in the cell102. The rheostat 112 is adjusted so as to represent the weigh of theperson whose blood alcohol is to be monitored. Other resistors may beincluded to control other factors and these particular matters aredisclosed in copending application Ser. No. 711,312. In the particularembodiment shown in FIG. 2, the switch 124 plays a part in the weightingof the information which is to be stored in the cell 100. Specifically,the length of time that the switch 124 is held down determines thequantity ofactive material which is stored in the cell 100.

As an example, each 10 seconds that the switch 124 is held down mayrepresent 1 ounce of standard 86-proof alcohol. It can be seen,therefore, that beverages such as wine, beer, brandy, rum, etc., wouldrequire that the switch 124 be held down for varying lengths of time inaccordance with the proof of the alcoholic beverage consumed and thequantity of the beverage. As an example, a drink containing 2 ounces of86- proof alcohol would require that the switch 124 be held down for 20seconds. On the other hand, 2 ounces of brandy which has a proofapproximately one-half of standard 86-proof alcohol would require thatthe switch 124 be held down for 10 seconds. The length of time,therefore, that the switch 124 is energized is a simple way ofdetermining the particular quantity of information which is stored bythe monitoring system of FIG. 2. The specific nature in which themonitor works in providing an approximation of the blood alcohol levelmay be seen with greater accuracy with reference to copendingapplication Ser. No. 771,312.

When the switch 124 is depressed, the source of voltage 106 provides fora flow of current through the storage cell 100 in a direction to providefor the storage of active material in representation of the quantity ofalcohol, the proof of the alcohol and the weight of the drinker. Whenthe desired time for the switch 124 to be held down expires, the switchis released and the cell 100 now contains the proper storage of activematerial representing the quantity of alcohol which would be present inthe blood if all of the alcohol is immediately absorbed into thebloodstream. The average person can assimilate alcohol in thebloodstream at a predetermined rate, and these details are all explainedfuller in the copending application Ser. No. 711,312.

The source of voltage 104 provides a current flow through the cell 100in a direction opposite to the current flow provided by the source ofvoltage 106. Also note that with the switch 126 in the position as shownin FIG. 2, the circuit including the source of voltage 104 and the cell100 includes a resistor 108 and the resistor 108 is chosen to have arelatively high value so that the current flow through the cell 100 isrelatively low and approximates the rate at which the body canassimilate the alcohol in the blood.

It can be seen, therefore, that each time the operator of the monitoringdevice of FIG. 2 takes a drink, he may depress the switch 124 for theappropriate length of time in representation of the proof and quantityof that drink and the cell 100 receives a transfer of a quantity ofactive material, which transfer is in a direction to represent anincrease in the level of alcohol in the blood. The source of voltage 104produces a counterflow of current through the cell 100 which representsa decrease in the level of alcohol in the blood. The counterflow ofcurrent, when extended for a long enough period of time, ultimatelyresults in all of the active material being transferred back within thecell 100 so as to represent an assimila tion of all of the alcohol inthe blood.

During the operation of the monitoring device of FIG. 2, it is oftendesirable to produce an output indication to the user of the monitoringdevice as to the level of alcohol in the blood. This readout should beprovided in a nondestructive way so that the operator of the devicecannot erase the information stored in the cell 100. The readout may beaccomplished by the use ofthe switches 126 and 128 which, as shown inFIG, 2,

are ganged together. These switches are moved to the read position so asto provide for the nondestructive readout of the present invention.

When the switch 126 is in the read position, the voltage source 104 isnow included in a circuit to produce a current flow through both thecells 100 and 102 and the resistor 116. The value of resistor 116 ischosen to be significantly less than the value of resistor 108 so thatthe voltage source 104 produces a current flow in a direction throughthe cell 100 so as to rapidly transfer all of the active material whichhas been stored in the cell in representation ofinformation. At the sametime the information is being removed from the cell 100, a comparableamount of information represented by a transfer of active material isstored in cell 102. When all of the information is removed from one ofthe electrodes in the cell 100, the resistance of the cell increases,thereby providing for a rise in voltage across the cell 100. Therefore,when the cell 100 has all of its active material removed from oneelectrode, the voltage at the base of the transistor 130 goes down toturn on the transistor 130.

Prior to the turning on of the transistor 130 and during the time thatthe cell 100 is being read out, the transistor 132 is turned on. Thetransistor 132 acts as a constant current source for the capacitor 152.The capacitor 152 normally has a voltage approximately equal to a valuesuch as 0.6 volt because of the voltage applied to the capacitor 152from the readout terminal of the switch 128 and through a voltagedivider network of resistors 136 and 140. When transistor 132 turns onto act as the constant current source, the voltage across the capacitor152 goes up in accordance with the length of time that the transistor132 is turned on.

The transistor 134 is adjusted to be off when the value of the capacitor152 is at or slightly below the normal voltage value across thecapacitor 152, for example, the 0.6 volt. When the transistor 132 isturned on to supply current to build up the voltage across the capacitor152, the transistor 134 is turned on as soon as the voltage across thecapacitor exceeds the normal value of, for example 0.6 volt. When thetransistor 134 is turned on, an output signal is now produced, whichoutput signal passes through the meter 150. The meter may be, forexample, an ammeter so that the meter 150 provides for an outputindication in accordance with the current flow produced by thetransistor 134. The transistor 134 is adjusted so that the output signalfrom the transistor 134 rises linearly in accordance with the rise involtage across the capacitor Since the transistor 132 supplies aconstant current to the capacitor 152, the voltage across the capacitorrises linearly. Therefore, as long as current flows through the cell toprovide for a readout of the cell 100, the meter 150 produces a risingoutput indication which represents the quantity of information which isstored in the cell 100. When all of the information is read out ofthecell 100 as indicated above, the resistance of the cell 100 changes toprovide an increase in voltage across the cell 100 which in turnprovides for a decrease in the voltage at the base of the transistor130. The decrease in voltage at the base of the transistor turns on thetransistor 130 which produces an output signal to turn off thetransistor 132.

When the transistor 132 is turned off, the transistor 132 no longer actsas a constant current source for the capacitor and the value of thevoltage across the capacitor 150 is, therefore, maintained at its lastvalueNThe flow of current through the meter from the transistor 134 isat a constant value so as to provide for an indication of the quantityof information that had been stored in the cell 100 which in turnrepresents the level of the alcohol in the blood of the user of themonitoring device of FIG. 2.

The resistor 114 is used as a protective device since the cell 100,before all of the active material is transferred from one of theelectrodes, has a relatively low resistance when compared with theresistor 114 and therefore almost all of the current produced by thevoltage source 104 flows through the cell 100. However, when the cell100 has all of the active material removed form one of its electrodes,the resistance rises and the resistor 114 is used to limit the currentand voltage across the cell 100 to protect the cell 100.

When the meter 150 reaches a steady-state condition, the user of thedevice of FIG. 2, therefore, knows that the device has provided for thefull readout and notes the level of the blood in the alcohol inaccordance with the output indication from the meter 100. After theoutput indication on the meter is noted, the switches 126 and 128 may beactivated back to their normal position as shown in FIG. 2. In thenormal position of the switches shown in FIG. 2, the capacitor 152 isquickly discharged through transistor 134, resistors 146 and 148 andmeter 150. The capacitor 152 drops to its normal level of approximately0.6 volt, which level is not sufficient to maintain the transistor 134on. The transistors 130 and 132 are also turned off since there is nosupply voltage to these transistors through the switch 128.

The series arrangement of the cells 100 and 102 now receives a currentfrom a source of low voltage 106 in combination with the diodes 118 and120. This current from the source of low voltage 106 is in a directionto discharge the ac tive material which had been stored during readoutin the cell 102 and to recharge the cell 100 in accordance with thequantity of active material which is stored in the cell 102. The currentflow from the source of low voltage 106 through the cells 100 and 102continues until all of the active material which was stored duringreadout in the cell 102 is removed from one of the electrodes. At thattime a comparable amount of active material had been restored in thecell 100 and this quantity of active material represents the activematerial which was stored in the cell 100 prior to the readout.

When all of the active material is removed from one electrode of thecell 102, the resistance across the cell 102 rises and this rise inresistance substantially limits the current through the cells 100 and102 to a negligible value. The circuit after the complete readout cyclenow continues to operate in the normal manner described above whereininformation may be stored by depressing the switch 124 and then thisinformation is removed at a constant rate in accordance with a currentproduced by the voltage source 104.

It is to be appreciated that the nondestructive readout circuit and themethod using the circuit may be used in other systems in addition to thesystem shown in FIG. 2 and that the invention is not to be limited tothe specific embodiment shown but that various adaptions andmodifications may be made. The invention, therefore, is only to belimited by the appended claims.

Ielaim:

1. A nondestructive readout for the electrochemical cell storage unit,including,

a first electrochemical cell and a second electrochemical cell connectedin series,

first terminal means for receiving a first current flow through thefirst electrochemical cell to store information in the firstelectrochemical cell,

second terminal means for receiving a second current flow through boththe first and second electrochemical cells,

third switch means connected to the second terminal means and with theswitch means having a first position to receive a readout current toread out the information stored in the first electrochemical cell and atthe same time to store the same quantity of information in the secondelectrochemical cell and with the switch means having a second positionto receive a restoring current to remove the information stored in thesecond electrochemical cell and to restore the information originallystored in the first electrochemical cell, and

fourth voltage source means having a value less than 0.5 volts coupledto the third switch means in the second position to provide therestoring current and with the third switch means normally in the secondposition.

2. A nondestructive readout for an electrochemical cell storage unit,including a first electrochemical cell storage unit including at leastfirst and second electrodes and including active material for transferbetween the first and second electrodes and with the firstelectrochemical cell having a first impedance value with active materialon both the first and second electrodes and with the firstelectrochemical cell having a second higher impedance value with activematerial only on the first electrode,

a second electrochemical cell storage unit including at least first andsecond electrodes and including active material for transfer between thefirst and second electrodes and with the second electrochemical cellhaving a first impedance value with active material on both the firstand second electrodes and with the second electrochemical cell having asecond higher impedance value with active material only on the frstelectrode,

first means coupled to the first electrochemical cell for providing afirst current flow through the first electrochemical cell in a firstdirection to store information by transferring active material from thefirst to the second electrode,

second means coupled to the first and second electrochemical cells forproviding a second current fiow through the first and secondelectrochemical cells in a second direction to read out the informationstored in the first electrochemical cell by retransferring all of theactive material stored on the second electrode to the first electrodeand at the same time transferring active material in the secondelectrochemical cell from the first to the second electrochemical cell,

third means coupled to the first and second electrochemical cells forproviding a third current fiow through the first and secondelectrochemical cells and with the third current flow in the samedirection as the first current flow through the first electrochemicalcell to transfer information from the first to the second electrode andwith the third current flow in a direction through the secondelectrochemical cell to transfer all of the active material stored onthe second electrode to the first electrode and with the third meansincluding a source of voltage having a value less than 0.5 volts andwith voltage across the second electrochemical cell rising toapproximately the value of the source of voltage when all of the activematerial stored on the second electrode of the second electrochemicalcell is transferred to the first electrode and with the third currentflow substantially eliminated when the voltage rises across the secondelectrochemical cell. 3. The nondestructive readout of claim 2 whereinthe third means is normally coupled to the first and secondelectrochemical cells while the first means is coupled to the firstelectrochemical cell.

4. A method of providing a nondestructive readout for a firstelectrochemical cell storage unit wherein the first cell includes atleast a pair of electrodes and an active material for transfer betweenthe electrodes in representation of information and a secondelectrochemical cell storage unit in series with first cell and with thesecond cell including at least a pair of electrodes and an activematerial for transfer between the electrodes including the steps of,

providing a first current flow through the first cell in a firstdirection to transfer active material in the first cell.

providing a second current flow, through the first and second cells in asecond direction opposite to the first direction to retransfer theactive material within the first call and to transfer active materialwithin the second cell to read out the first cell, and

providing a low-voltage source normally across the first and secondcells to produce a third current flow through the first and second cellsand with the third current flow in the same direction through the firstcell as the first current flow and with the third current flowretransferring the active material in the second cell and transferringthe active material in the first cell.

5. The method of claim 4 additionally including the step of monitoringthe second current flow to provide an output indication of the quantityof active material which was transferred due to the first current flow.

6. A method of providing a nondestructive readout for a firstelectrochemical cell and with the first electrochemical cell connectedin a circuit including the first electrochemical cell and a secondelectrochemical cell in series and with a first set of terminals coupledto the first cell and with a second set of terminals coupled to theseries arrangement of the first and second cells and with a low-voltagesource coupled across the second set of terminals to provide a currentflow through the first and second cells in a first direction, includingthe steps of,

providing a first current to the first set of terminals to provide afirst current through the first cell in the first direction to recordinformation in the first cell,

providing a second current to the second set of terminals to provide asecond current through the first and second cells in a second directionopposite to the first direction to read out the information in the firstcell and with the current provided by the low-voltage sourceautomatically restoring the information in the first cell when thesecond current is discontinued.

7. The method of claim 6 additionally including the step of monitoringthe second current to provide an output indication of the informationrecorded in the first cell.

8. Apparatus for providing a nondestructive readout of anelectrochemical storage cell, including first and second electrochemicalcells in series,

first means for providing a first current in a first directionrepresentative of information through the first cell,

second means for providing a second readout current in a second oppositedirection through the first and second cells, third means including asource of voltage having a value less than 0.5 volts for providing athird restoring current in the first direction through the first andsecond cells, and

switching means coupled to the second and third means for additionallycoupling the second and third currents through the first and secondcells.

9. The apparatus of claim 8 additionally including means for monitoringthe second readout current to provide an output indication oftheinformation in the first cell.

1. A nondestructive readout for the electrochemical cell storage unit,including, a first electrochemical cell and a second electrochemicalcell connected in series, first terminal means for receiving a firstcurrent flow through the first electrochemical cell to store informationin the first electrochemical cell, second terminal means for receiving asecond cUrrent flow through both the first and second electrochemicalcells, third switch means connected to the second terminal means andwith the switch means having a first position to receive a readoutcurrent to read out the information stored in the first electrochemicalcell and at the same time to store the same quantity of information inthe second electrochemical cell and with the switch means having asecond position to receive a restoring current to remove the informationstored in the second electrochemical cell and to restore the informationoriginally stored in the first electrochemical cell, and fourth voltagesource means having a value less than 0.5 volts coupled to the thirdswitch means in the second position to provide the restoring current andwith the third switch means normally in the second position.
 2. Anondestructive readout for an electrochemical cell storage unit,including a first electrochemical cell storage unit including at leastfirst and second electrodes and including active material for transferbetween the first and second electrodes and with the firstelectrochemical cell having a first impedance value with active materialon both the first and second electrodes and with the firstelectrochemical cell having a second higher impedance value with activematerial only on the first electrode, a second electrochemical cellstorage unit including at least first and second electrodes andincluding active material for transfer between the first and secondelectrodes and with the second electrochemical cell having a firstimpedance value with active material on both the first and secondelectrodes and with the second electrochemical cell having a secondhigher impedance value with active material only on the first electrode,first means coupled to the first electrochemical cell for providing afirst current flow through the first electrochemical cell in a firstdirection to store information by transferring active material from thefirst to the second electrode, second means coupled to the first andsecond electrochemical cells for providing a second current flow throughthe first and second electrochemical cells in a second direction to readout the information stored in the first electrochemical cell byretransferring all of the active material stored on the second electrodeto the first electrode and at the same time transferring active materialin the second electrochemical cell from the first to the secondelectrochemical cell, third means coupled to the first and secondelectrochemical cells for providing a third current flow through thefirst and second electrochemical cells and with the third current flowin the same direction as the first current flow through the firstelectrochemical cell to transfer information from the first to thesecond electrode and with the third current flow in a direction throughthe second electrochemical cell to transfer all of the active materialstored on the second electrode to the first electrode and with the thirdmeans including a source of voltage having a value less than 0.5 voltsand with voltage across the second electrochemical cell rising toapproximately the value of the source of voltage when all of the activematerial stored on the second electrode of the second electrochemicalcell is transferred to the first electrode and with the third currentflow substantially eliminated when the voltage rises across the secondelectrochemical cell.
 3. The nondestructive readout of claim 2 whereinthe third means is normally coupled to the first and secondelectrochemical cells while the first means is coupled to the firstelectrochemical cell.
 4. A method of providing a nondestructive readoutfor a first electrochemical cell storage unit wherein the first cellincludes at least a pair of electrodes and an active material fortransfer between the electrodes in representation of information and asecond electrochemical cell storage unit in series with first cEll andwith the second cell including at least a pair of electrodes and anactive material for transfer between the electrodes including the stepsof, providing a first current flow through the first cell in a firstdirection to transfer active material in the first cell. providing asecond current flow, through the first and second cells in a seconddirection opposite to the first direction to retransfer the activematerial within the first call and to transfer active material withinthe second cell to read out the first cell, and providing a low-voltagesource normally across the first and second cells to produce a thirdcurrent flow through the first and second cells and with the thirdcurrent flow in the same direction through the first cell as the firstcurrent flow and with the third current flow retransferring the activematerial in the second cell and transferring the active material in thefirst cell.
 5. The method of claim 4 additionally including the step ofmonitoring the second current flow to provide an output indication ofthe quantity of active material which was transferred due to the firstcurrent flow.
 6. A method of providing a nondestructive readout for afirst electrochemical cell and with the first electrochemical cellconnected in a circuit including the first electrochemical cell and asecond electrochemical cell in series and with a first set of terminalscoupled to the first cell and with a second set of terminals coupled tothe series arrangement of the first and second cells and with alow-voltage source coupled across the second set of terminals to providea current flow through the first and second cells in a first direction,including the steps of, providing a first current to the first set ofterminals to provide a first current through the first cell in the firstdirection to record information in the first cell, providing a secondcurrent to the second set of terminals to provide a second currentthrough the first and second cells in a second direction opposite to thefirst direction to read out the information in the first cell and withthe current provided by the low-voltage source automatically restoringthe information in the first cell when the second current isdiscontinued.
 7. The method of claim 6 additionally including the stepof monitoring the second current to provide an output indication of theinformation recorded in the first cell.
 8. Apparatus for providing anondestructive readout of an electrochemical storage cell, includingfirst and second electrochemical cells in series, first means forproviding a first current in a first direction representative ofinformation through the first cell, second means for providing a secondreadout current in a second opposite direction through the first andsecond cells, third means including a source of voltage having a valueless than 0.5 volts for providing a third restoring current in the firstdirection through the first and second cells, and switching meanscoupled to the second and third means for additionally coupling thesecond and third currents through the first and second cells.
 9. Theapparatus of claim 8 additionally including means for monitoring thesecond readout current to provide an output indication of theinformation in the first cell.